Souta Matsusaka

Adhesional bonding of fine gold wires to metal substrates

The transition from the adhesional elastic contact to the elasto-plastic contact is discussed, using Au wires as cylindrical bodies. The simple compensation for elasto-plastic contact was numerically carried out to obtain smooth transition profiles from elastic to elasto-plastic contact, depending on the applied force f. Au wires with a diameter of 100 μm were contacted to Au plates and Si substrates after they were irradiated with Ar+ ions. It was found that the experimental contact width 2a was nearly equal to the theoretical adhesional elastic contact width 2aj when f was small enough (f < 500 N/m) but the contact width 2a gradually became greater than 2aj as f increased (f > 500 N/m), and became nearly equal to the elasto-plastic contact width a ep . On the other hand, the actual fracture strength was much less than the theoretical fracture (pull) strength of the adhesional contact and it was also found that the experimental bond strength increased with increasing the holding time after bonding (contacting).

Moving force of metal particle migration induced by laser irradiation in borosilicate glass

We optically manipulated a metal particle in borosilicate glass. The glass in the neighborhood of the laser-heated metal particle softened; hence, the metal particle was able to migrate in the glass. In this letter, the driving force of the metal particle toward the light source in the glass provided by laser illumination was investigated. The variation in the surface tension of the glass at the interface between the glass and the metal particle induced by the temperature gradient was calculated via a numerical temperature calculation. It was found that the temperature at the laser-illuminated surface of a stainless-steel particle with a radius of 40 μm was ~320 K higher than that on the nonilluminated side. The force applied to the metal particle from the surrounding glass was calculated to be ~100 μN, which was approximately equal to the viscous resistance force. In addition, the experimental and numerically calculated speeds of the moving particle, which was measured while varying the laser power, are discussed.

Formation of a buried silver nanowire network in borosilicate glass by solid-state ion exchange assisted by forward and reverse electric fields

Using electric-field-assisted solid-state ion exchange, we formed a buried silver nanowire network in borosilicate glass. This procedure had two stages: a silver doping stage by applying voltage with silver as the anode (referred to as forward) and a silver precipitation stage by applying voltage in the opposite direction (referred to as reverse). Microscopic observations revealed many needle-like precipitates (100–300 nm in diameter) linked to each other, forming a thin layer at the bottom of the silver-doped area. The configuration of the layer formed in the glass matrix was precisely transferred from that of the dopant, silver foil in the present study. The embedded electrical wiring in the glass slide was tested using a patterned circuit-like silver foil as a dopant. Measuring the electrical resistance between two ends of the formed wire, we found that the embedded layer had high conductivity and acted as an electrical circuit.

Laser-Arc Hybrid Welding Process of Galvanized Steel Sheets

Galvanized steel sheets with a lap joint were welded by a laser-arc hybrid process. The hybrid system consisted of 2kW LD or YAG laser oscillator and frequency-modulated DC pulsed MAG welding machine. In this experiment, the arc traveled on the specimens, following the laser beam with the interval of 2 mm. The results showed that the hybrid process had some advantages, such as deep penetration depth, high welding speed and high gap-tolerance, in comparison with the conventional MAG welding. Observations from a high-speed digital video-camera suggested that the zinc and iron vapors induced by laser beam irradiation stabilized the arc plasma. Effects of the incidence angle between a welding head and a specimen on the weld bead formations were also discussed. As a result, the welding speed of 2.0 m/min was achieved at 1.0 mm of gap length condition when the incidence angle was 50 degree.

Experimental and theoretical study on the driving force and glass flow by laser-induced metal sphere migration in glass

Light is able to remotely move matter. Among various driving forces, laser-induced metal sphere migration in glass has been reported. The temperature on the laser-illuminated side of the sphere was higher than that on the non-illuminated side. This temperature gradient caused non-uniformity in the interfacial tension between the glass and the melted metal as the tension decreased with increasing temperature. In the present study, we investigated laser-induced metal sphere migration in different glasses using thermal flow calculations, considering the temperature dependence of the material parameters. In addition, the velocity of the glass flow generated by the metal sphere migration was measured and compared with thermal flow calculations. The migration velocity of the stainless steel sphere increased with increasing laser power density; the maximum velocity was 104 μm/s in borosilicate glass and 47 μm/s in silica glass. The sphere was heated to more than 2000 K. The temperature gradient of the interfacial tension between the stainless steel sphere and the glass was calculated to be −2.29 × 10−5 N/m/K for borosilicate glass and −2.06 × 10−5 N/m/K for silica glass. Glass flowed in the region 15–30 μm from the surface of the sphere, and the 80-μm sphere migrated in a narrow softened channel.

Laser-induced nickel sphere migration and nanoparticle precipitation in silica glass

Techniques to control the colors and properties of glasses based on doping of the glasses with various metals and nanoparticles are widely used. In this paper, we demonstrate the migration of a nickel sphere in silica glass caused by laser illumination accompanied by nickel nanoparticle precipitation in the sphere migration trajectory. During migration, the diameter of the nickel sphere decreased. Precipitated nanoparticles with diameters of several hundred nanometers were observed in areas of up to 50 μm in radius and these nanoparticles formed four cylindrical coaxial layers with stripes at 10–20 μm intervals in the migration direction.

Selective component nanoparticle precipitation from Invar 42 during metal particle migration by laser irradiation in silica glass

ABSTRACT Laser illumination on a nickel sphere in silica glass has shown to migrate the sphere towards the light source with a nickel nanoparticle precipitated around the sphere. The selective nanoparticle precipitation by Invar 42 sphere migration in silica glass is reported. An Invar sphere is implanted into glass by laser illumination of an Invar foil. In addition to the sphere migration in glass, stripes are formed along the trajectory of the sphere. The stripes consist of metal nanoparticles with a diameter of several hundred nanometres. Nanoparticles precipitated on the laser-illuminated side are composed only of nickel and those on the non-illuminated side are composed of nickel and iron alloys. The reason for the difference in components is discussed.

Transmittance properties and TEM observation of metal doped glass by field-assisted ion exchange

Metal (silver or copper) ions were doped into borosilicate glass using an electric field- assisted ion exchange method. The optical transmittance of the metal doped glass was measured to determine why the doped glass exhibited an excellent laser micro-machinability. The doped metal ions were found to have enhanced the optical absorption of the glass, especially in the ultraviolet range. This in turn facilitated the efficient absorption of incident laser irradiation, and hence improved laser machinability of the glass. The metal doped glass also exhibited some absorption in the visible range, leading to a slight yellow-brown coloration. Transmission electron microscope (TEM) observations indicated that the metal ions had penetrated the glass and therein formed nanometer-sized (~6 nm) fine particles. In an attempt to control the optical characteristics in the ultraviolet-visible range, metal doped glass was heat-treated following the ion exchange doping step. In the case of silver-doped glass with heat treatment at 723 K, silver nanoparticles aggregated locally yielding an inhomogeneous structure. The heat-treated samples had a high optical absorption in the ultraviolet range.

Contact Probe Card with Large Overdrive

G. Kimoto , T. Watanabe, T.Kuroda, S. Matsusaka, and M. Saito Graduate School & Faculty of Engineering, Chiba University, Yayoi-cho, Inage, Chiba, Chiba 263-8522, Japan Kisarazu National College of Technology, KiyomidaiHigashi, Kisarazu, Chiba 292-0041, Japan Nanotechnology Research Center, Waseda University, Wasedatsurumaki-cho, Shinjuku, Tokyo 162-0041, Japan Probeace Co., Ltd., Ariake, Koutou, Tokyo 135-0063, Japan

New Development of Contact Probe and Methodology

We present a new type of wafer probe card with resin film consisting of two beams. Resin film is embedded on both sides of the probe beam, having a thickness of 4 [μm] and made from polyimide. This proposed probe enables compliant structures with large overdrive to ensure high durability of the structure and controllable scrub motion to assure cleaning process. In this study, Matrix method is introduced for theoretical studies of the probe structure and commercial finite element code is used. Electrical contact resistance is determined by theoretical studies based on Holms theory and experimentally by　our measurement instrumentation respectively. The structure is proven theoretically to get appropriate scrub motion when it undergoes a large overdrive with preferable exhibited contact force. Moreover, all of these mechanical characteristics can be varied to know the values of the character of probes. The methodology having one of the most preferable characters of the contact-probe had been achieved.